JPH0820663B2 - Automatic metering exposure control device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an improvement of an automatic exposure control device for a camera of an instantaneous aperture metering system.

(Background of the Invention) In a conventional instantaneous aperture metering system camera, photometry is performed through a taking lens prior to the instant aperture operation, the aperture value is determined from the result of the photometry, and the aperture is stopped down to the determined aperture value. The shutter is controlled based on the result of photometry through the photographing lens after that. However, no solution has been found for obtaining a proper exposure for a high-brightness subject. For example, in the open metering system, there was a technology to control the photometric value by replacing it with the limit value at the photometric limit, but in the instantaneous aperture metering system, there was a problem that the shutter could not be controlled if the photometric value was replaced with the photometric limit value. .

(Object of the Invention) An object of the present invention is to provide an automatic exposure control apparatus of a squeezing metering system capable of performing appropriate exposure control even for a high-brightness subject.

<Example> Fig. 1 (a) is an example of division of a field scene screen of a multi-photometric device according to the present invention, which is a five-division screen constituted by a central portion and a four-divided peripheral portion. is there. Fig. 1 (b)
Is a modified example of FIG. 1 (a), in which the sensitivity of the central portion is expanded to the lower portion. Although there are various division methods, this division method keeps the balance between the circuit complexity and the effect of multi-photometry (Act No. 55-125623).

In order to explain the following embodiments, the central portion is Z ₀ , and the upper left, upper right, lower left, and lower right are Z ₁ , Z ₂ , Z ₃ , and Z ₄ in order.

FIG. 2 shows a photometric optical system. 1 is a photographing lens, 2 is a diaphragm, 3 is a quick return mirror, 4 is a shutter, 5 is a film surface, 6 is a finder screen, and 7 is a pentaprism. An eyepiece lens (not shown) guides the light emitted from the prism 7 to the photographer's eye, and the photographer receives the light and can observe the field screen. 8, 9 and 10 are one set on both sides of an eyepiece lens (not shown), 8 is a triangular prism,
9 is a condenser lens, 10 is a silicon photodiode (hereinafter
SPD). FIG. 3 is a SPD pattern for realizing the division of FIG. 1 (b). Z _{0 to} Z ₄ correspond to FIG. 1 (b), respectively, and the central part Z ₀ has left and right SPs.
D is connected in parallel. That is, a and a ', b and b'
Is connected.

FIG. 4 is a detailed block diagram of the embodiment of the present invention.
The photometering circuits 100 to 104 are known photometering circuits, each of which is composed of an SPD, a reference voltage source, a log diode, and an OP amplifier. The metering areas Z _{0 to} Z ₄ shown in FIG. Get PV _{0 to} PV ₄ . Further, the photometric circuit 100 improves the photometric accuracy by connecting in parallel the parts corresponding to the central region of the left and right SPDs, as shown by the SPD pattern in FIG.
It is also used as a monitor photometric output when controlling the aperture and shutter by the instantaneous aperture metering method, and the photometric output after release changes according to the aperture value AV and becomes BV ₀ -AV.
BV ₀ is the brightness value of the central part to be monitored. The potentiometers 105 to 108 are respectively set to the shutter speed value TV _M ,
Aperture value AV ₀ , set aperture value A _M- AV ₀ (where A
V _M is an aperture value that is manually set) and a film sensitivity value SV, and generates an analog amount corresponding to each set value. 109 is a mode setting means, and when the aperture priority mode (A mode), the mode switch S _W5 is
FF and a connexion, becomes its output is "H" level, shutter priority mode (S mode) Modosuitsuchi S _W5 is ON and a connexion time, its output becomes "L" level.

120 P ₃ to P ₀ by connexion is set to the output terminal "9" of at microcomputer Units - in analog switch circuit (hereinafter referred to as MCU 122), "8", ..., "1", "0" Therefore, the analog amount of the corresponding input terminals “9” to “0” is transmitted to the “OUT” terminal. 121 is a 6-bit A / D converter that converts the analog amount selected by the analog switch circuit 120 into a digital value and outputs the upper 2 bits to the MCUR ₉ and R ₈ terminals and the lower 4 bits.
It is transmitted to bit to K ₃ ~K ₀ pin.

123 and 124 MCU of R ₅ ~ in each 6-bit D / A converter
Generates an analog amount set by the output of the R ₀ terminal and the R _{15 to} R ₁₀ terminals, and a reference of $ 18 + TV during diaphragm control.
_{It is M} -SV (*) ($ indicates hexadecimal) and the film sensitivity setting value ($ 33-SV (*)) during shutter control. (SV (*) is the film sensitivity value after correction by multi-photometry and will be described in detail later).

155 R ₆ terminal of release after MCU122 by the diaphragm control means L
When it becomes, it becomes active. Metering output PV ₀ '(= BV ₀ -AV) while narrowing down the metering circuit 100 to the non-inverting input terminal
, And the reference output $ 18 + TV _M −SV (*) of the D / A converter 123 is input to the inverting input terminal.

BV ₀ −AV ≦ $ 18 + TV _M −SV (*) (1) Stopping the stop The magnet 156 is energized to stop the stop. When the aperture value at this time is AV _S, the _{BV 0 -AV S = $ 18 +} TV M -SV (*) (2). SV
(*) Is the film sensitivity value after correction by multi-photometry, which has the relationship of SV (*) = (BVans-BV ₀ ) + SV (3), and the brightness value BVan calculated by multi-photometry
The difference between s and the brightness value of the central portion is set as a correction amount and added to the film sensitivity value SV. From equations (2) and (3), BV ₀ −AV _S = $ 18 + TV _M − (BVans−BV ₀ ) −SV (4) BVans + SV = $ 18 + TV _M + AV _S (4) ′ is obtained. Since $ 18 is the shift for circuit convenience,
(4) set from 'film speed value SV, it can be seen that controlled by the aperture value AV _S as a proper luminance value BVans the set shutter speed value TV _M.

Since the analog amount of ($ 33-SV (*)) set in the D / A converter 124 is added to the non-inverting input terminal of the OP amplifier 160, it is connected to the inverting input terminal of the OP amplifier 160 and the emitter of the transistor 162. One end of the resistor 161 has the same potential as ($ 33-SV (*)). Also, other predetermined value stop after the release of the photometric circuit 100 to the terminal of the resistor 161 photometric output of the central portion of the case has decreased to (AV _M or _{AV S) (BV 0 -AV M} ) or (BV ₀ −A
V _S ) to enter. Therefore, the potential difference across the resistor 161 is ($ 3
3-SV (*)) - a _{{BV 0 -AV M (AV S} )}. Where (3) Applying equation _{$ 33- (BVans-BV 0)} -SV- {BV 0 - (AV M (AV S)} = $ 33- {BVans + SV-AV M (AV S)} = $ 33 -TV
It becomes _S (5). Here TV _S intended to satisfy _{BVans + SV = AV M (AV} S) + TV S (6), shutters as a proper exposure (BVans + SV) relative aperture value AV _M (or AV _S) narrowed down before Miraatsupu It is a speed value. If the hFE of the transistor 162 is high, almost equal currents flow through the resistors 161 and 163. Therefore, if the resistance values of the two are equal, the potential difference across the resistor 163 is also $ 33-T.
It corresponds to V _S. 160 to 163 work as a shutter speed value calculation circuit.

Mirror switch S _W2 turns off when the mirror is up, and turns on after the mirror goes down. Therefore, when the mirror switch S _W2 is turned off for a predetermined time of the release operation, the shutter speed calculation output ($ 33-TV _S ) immediately before the mirror up is stored in the memory capacitor 165.
Is stored.

Switch S _W3 is turned ON comparator 171 becomes the operating state at the time of Miraatsupu. At this time, the trigger switch S _{W4, which} is turned off in synchronization with the traveling of the shutter front curtain, is still on, so the output of the comparator 171 that is in the activated state is “L” and the shutter magnet 180 is energized, and the trigger switch is turned on. By the time S _W4 is turned off, the shutter retains the rear curtain by mechanical members and retains the rear curtain. When the front curtain precedes and the trigger switch _SW4 turns off, the timer capacitor 170
Is charged by the current source 172, and a voltage corresponding to the exposure time is generated across the capacitor 170. Memory capacitor
Corresponding to the potential of $ 33-TV _S stored in 165, the output of the comparator 171 is output when the electric charge is accumulated in the capacitor 170 for a short time at the time of high-speed second (when TV _S is large). Inversion, the energization of the shutter magnet 180 is released, the locking of the rear curtain is released, and the shutter is controlled at a predetermined shutter time. When TV _S is small, the capacitor 170 requires charging time and is controlled at low speed.

The resistor 125 and the capacitor 126 are input to the ▲ ▼ terminal of the MCU 122, and reset when the power is turned on. The capacitors 127 and 128 and the oscillator 129 are connected to the “Xtal” and “EXtal” terminals of the MCU 122, and the reference oscillation is generated by the internal oscillation circuit. The resistors 130 and 131 and the capacitor 132 form a differentiating circuit of the release switch S _W1 and are connected to the ▲ ▼ terminal of the MCU 122, so that the interrupt is performed when the release is performed.

Each of the LEDs _{7 to} LED ₀ has a cathode side connected to the O ₇ -O ₀ terminals of the MCU 122 and an anode side connected to a power supply via a resistor 140. When one of the O ₇ -O ₀ terminals of the MCU 122 becomes L, one of the LEDs ₇ to LED ₀ lights up. These LED arrays, when the Modosuitsuchi S _W5 interlocked with the exposure mode selecting member (not shown) of the Yotsute A mode "1000" - ... "LT" ,
When the display film of is in S mode, "F16", "F1"
The display film of "1", ... "F1.4" is selected and can be visually recognized in the finder. The MCU 122 is a 4-bit microcomputer, and the internal configuration is shown in FIG.

In the figure, the ROM in which the instructions for the arithmetic unit ALU and MCU are written, and the program counter P that specifies the address of the ROM
Instruction decoder DE that translates C and ROM instructions
C, control logic unit C that executes translated instructions
It is composed of a RAM that functions as a register designated by L, X, and Y, an oscillation circuit OSC, output-only ports P and O, an input-only port K, an input / output port R, and a timer T. Such microcomputers include the MB8850 series manufactured by Fujitsu. Also, a part of RAM is used as shown in Table 1. Since a part of this RAM is a 4-bit microcomputer, there is a part where a 2-word 8-bit data memory is used as one register, and that part is shown with a suffix Z.

FIG. 6 is a flow chart of the MCU 122. First, in the information input subroutine, the open metering output of the metering circuits 100-104
Enter PV _{0 to} PV ₄ and the setting information for each setting method. Next, by the subroutine of multi-photometry calculation, the appropriate brightness value BVans
Is calculated, and the corrected film sensitivity value SV (*) is calculated. Then, it is determined whether the S mode or not, and the A mode operation or the S mode operation is performed.

In the S mode, the mode switch _SW5 is turned on, the output of the setting means 109 becomes "L" level, and "$ 00" is stored in the RAM register _Z09 . On the other hand, in the A mode, the mode switch _SW5 is turned off and the output of the setting means 109 is "H".
Then, "$ 3F" will be stored in Z ₀₉ . Yotsute Z ₀₉ 2
⁵ is a digit M [1,9] (where M [a, b] with X register a, Y register is represented as a data memory for 4 bits of RAM that is specified when the b) 2 ¹ Yotsute to a checking digit, M [1,9] ₁ = 0 (7) (where M [a, b] that subscript n of _n is 2 ^n-th digit of the memory of the data memory (Shown) is the S mode. Further, when M [1, 9] ₁ = 1 (8), the A mode is set. According to M [1,9] ₁ , S
When the mode operation or the A mode operation is performed, the display operation is performed.

Next, set Z1 _F ← $ 33 (9) and calculate Z _1F ← Z _1F -Z ₁₈ (10). Since the Z ₁₈ SV (*) has been stored before this, the register _{Z 1F $ 33-SV (*} ) is excisional. Register Z _1E , Z _1F after disabling interrupt once
2 ^{5-2 0} of digit information that is stored in the $ 18 + TV _M -SV
(*), Of each $ 33-SV the _{(*) MCU122 R 5 ~R 0} R
Output to _{15 to} R ₁₀ terminals, $ 18 to D / A converter 123 and 124
Set + TV-SV (*) and $ 33-SV (*).

Next, the interrupt prohibition is released and the processing from the start address is repeated. The reason why interrupts are prohibited when the registers Z _1E and Z _1F are output is to prevent release interrupts during updating of the D / A converters 123 and 124.

FIG. 7 is a subroutine of interrupt processing when due connexion release Sui Tutsi S _W1 in operation is ON and a connexion of MCU 122 ▲ ▼ terminal has fallen to "L" of Shiyatsutabotan. Register Z
_Set the bit of M [3, E] ₃ which is the 2 ⁷ digit of _1E to the R ₆ terminal. Then, after the time with a margin in the maximum time required for narrowing down by the internal timer, for example 70 ms, R ₆
Set the terminal to H level. M [3, E] ₃ functions as a flag for whether or not to control the aperture, and since it is set to 1 in the A mode, an H level output appears at the R ₆ terminal, and the aperture control means 155 operates. not activated, it is narrowed down to the set aperture value AV _M. On the other hand, in the S mode, since it is set to 0, the aperture control is performed after release, so that the magnet 156 is not energized before release.

FIG. 8 is a flow chart of a subroutine for inputting information. The P port is set to 9, the Y register is set to 9, and the 4 bits of the K port are stored in M [0,9].
Clear [1, 9]. To excisional input R _9, R ₈ terminals 2 ¹ and 2 M [1,9] _{1 0} ⁰ for M [1,9]. The value of P and Y is decremented by 1 and the above operation is performed with M [1, Y],
M [0, Y] when Yotsute Y has come negative and Te summer $ F to be repeated for Table 1 of Z ₀₉ to Z ₀₀ registers will have been excisional. That is, Z ₀₉ has mode information, Z
Film sensitivity value [SV] at ₀₈ , set at Z ₀₇
V _M- AV ₀ ], Z ₀₆ to open aperture value [AV ₀ ], Z ₀₅ to set shutter speed value [TV _M ], and Z _{04 to} Z ₀₀ to 5 metering outputs [P
V ₄ ] to [PV ₀ ] are stored.

Finally, by setting Z ₀₇ ← Z ₀₇ + Z ₀₆ (11), the register Z ₀₇ has [AV _M ] ← [AV _M- AV ₀ ] + [AV ₀ ] (11) ' The value [AV _M ] is stored.

FIG. 9 is a flow chart of a subroutine of multi-photometry calculation. Although one proper brightness value BVans is calculated from five photometric outputs PV ₄ -PV ₀ , the simplest example shows a method of obtaining the average photometric output PV _M.

Δ = PV _M -PV ₀ obtains a correction amount delta as (12), determine the SV (*) = Δ + SV (13) as the corrected film sensitivity value SV (*).

Next, find the write-value LV (hereinafter referred to as LV value) as follows.

_{LV = PV M + AV 0 +} SV (14) In addition, as the average photometric output PV _M is _{PV M = BV M -AV 0 (} 15), partial low value corresponding to the open aperture value AV ₀ with respect to the average luminance value BV _M Is. Calculate the LV value from equation (14) and store it in register Z _1C .

FIG. 10 is a flow chart of the S mode operation subroutine. First, by setting Z _1E ← $ 18 (16), 0 is set in M [3, E] ₃ to set the aperture control mode and the shift amount is set. Next, add the register Z ₀₅ that stores the set shutter speed value TV _M to the corrected film sensitivity value SV.
By subtracting (*), Z _1E ← $ 18 + TV _M- SV (*) (17). On the other hand, the register Z _1C that stores the LV value is subtracted from the register Z ₀₅ to obtain Z _1C ← LV-TV _M = AV _S (18). Next, compare with the register Z ₀₆ that stores the open aperture value AV ₀ , and if Z _1C <Z ₀₆ (= AV ₀ ) (19), then Z _1C ← Z ₀₆ (= AV ₀ ) (20) and set one Compared with the stored register Z _{07 of} aperture value A V _M , if Z _1C > Z ₀₇ (= A V _M ) (21) is established, Z _{1 C} ← Z ₀₇ (= A V _M ) (22) The range of data stored in _1C is A
Limited to V ₀ ~ A V _M. Since Z _1C is a 1 / 3EV step, subtract 3 corresponding to one step to display from F1.4 (AV = 1) as shown in FIG. 4 as Z _1C ← Z _1C -3 (23).

 FIG. 11 shows a subroutine for A mode calculation.

By setting Z _1E ← $ 80 (24), M [3, E] ₃ = 1, and after release, the R ₆ terminal remains H and the diaphragm control circuit 155 does not operate. Therefore, the diaphragm is narrowed down to the set diaphragm value. Be done. Further, pulling the register Z ₀₇ that stores the set aperture value AV _M from the register Z _1C which stores the LV value, obtain _{Z 1C ← LV-AV M =} TV S (25). Also, as Z _1C ← Z _1C- $ 09 (26), subtract $ 09 corresponding to 3 steps to represent the time longer than 1/8 second as "LT". The Yotsute Z _1C numerical value of 0 to $ 15 is stored.

 FIG. 12 shows a display calculation subroutine.

By changing Z _1C ← Z _1C / 3 (27) to one step, check Z _1C > 7 (28), and when Eq. (28) holds, Z _1C ← 7 (29). , Z ₇ is set to one of 0 to 7. Next, set CF ← 0 (30) Z _1D ← $ FF (31) to reset the carrier flag CF and set 0.
Port 0 _{7-0 0} and excisional "1" to all of the 8 bits of the register Z _1D for controlling the output, performs ROL process. The ROL process is a process of rotating 8 bits of Z _1D including the carry flag CF by 1 bit to the left. That is, Is performed. If this is done once, CF = 1 (32) Z _1D = 11111110B (33). B represents a binary number. By subtracting ₁ from register Z _1C and repeating the ROL process until Z _1C becomes negative, according to 0 to 7 stored in Z _1C , Z _1D has
"11111110B", "11111101B", ... "01111111B" are set. Therefore, when Z _1D is output from 0 _{7 to} 0 _O terminals, Z _1D
The LED designated by the bit whose L becomes L turns on and “F
1.4 "" F2 ", ..." F16 "or" LT "," 15 ", ..." 100
One point of the 0 "film board is indicated.

FIG. 13 is a flow chart of multi-photometry calculation. The BV conversion in the first step is to convert the photometric outputs PV _{4 to} PV ₀ stored in Z _{04 to} Z ₀₀ in Table 1 into brightness values BV _{4 to} BV ₀ and convert them to Z _{14 to} Z _10.
Store at. In the second step, the central brightness value BV ₀ used for monitoring the aperture control and shutter control is a value that is cut without being added to the calculation in the multi-photometric calculation, that is, a predetermined value (for example, EV16 when BV11 is ISO100. Value that is equal to or higher than the lower limit value of the photometry, or less than the lower limit value of the photometry, the brightness value that is necessary to control the aperture by the instantaneous aperture metering.
Stores in the save register Z ₁₅ in order to secure the BV _0, represents the BV ₀ which is the retracted with BV ₀ (*). In the subsequent third step, the cutting process is performed to cut the data in the area where the brightness value is equal to or higher than the predetermined value or equal to or lower than the measurable lower limit value. Fourth
Step it steps proper luminance value BVans calculated, but here performs simplest average brightness value BV _M calculated optimum luminance value B
Let's call it Vans.

As a result, BV _M is stored in register Z _18. The fifth step is to transfer the BV _M register Z ₁₈ in register Z _1C.
By subtracting BV ₀ (*) of the register Z ₁₅ from Z _{18 in} the sixth step, Δ = BVans (= BV _M ) −BV ₀ (*) (34) is stored in the register Z ₁₈ . This corresponds to the equation (12), and the function as the correction amount obtained by the multi-photometric calculation is the same. By adding the film sensitivity value SV of the register Z _{08 to} the register Z ₁₈ in the seventh step, the corrected film sensitivity value SV (*) of the equation (13) is stored in the register Z ₁₈ .

FIG. 14 is a flow chart of an embodiment of the present invention. The first step is a step for checking whether or not the photometric output PV _{0 in the} central portion reaches the upper limit value of A / D conversion. Since the A / D converter 121 in FIG. 4 has a 6-bit configuration, the upper limit is $ 3F, and the upper limit remains at $ 3F, so whether [PV ₀ ] = $ 3F (35) holds. Check. When expression (35) is satisfied, Z _1C ← $ 7F (36) Set the upper limit value in the display register Z _1C, and set register Z ₁₈ to $ F4 (=-$ C) corresponding to -4 [EV]. After setting, AV _{0 of the} register Z ₀₆ is subtracted and Z ₁₈ ← $ F4-Z ₀₆ (37) is set, so that the register storing the correction amount Δ corresponds to − (4 + AV ₀ ) [EV]. Set value, SV
Jump to the step that asks for (*). This (36),
The meaning of the step in equation (37) will be described later.

The second step is a step for checking whether or not the photometric output PV _{0 in the} central portion becomes the lower limit value of A / D conversion and reaches the lower limit value of photometry.

When [PV ₀ ] = $ 00 (38) holds, set _Z1C ← $ 00 (39) to the display register Z _1C to set the lower limit value, and set Z ₁₈ ← $ 00 (40). Then, a value corresponding to 0 [EV] is set in the register for storing the correction amount Δ and jumped to the step for obtaining SV (*). The meaning of these (39) and (40) steps will be described later. From the third step onwards, the first step in FIG. 13 is performed.
It is the same as that after step.

FIG. 15 is a flow chart of the BV conversion subroutine of FIGS. 13 and 14. The photometric outputs PV _{4 to} PV ₀ are lower than the brightness value BV ₄ −BV ₀ of the object field by the amount corresponding to the decrease in the light amount due to the open aperture value AV ₀ . Then, the photometric output is converted into an absolute luminance value. Therefore, if the value exceeds the predetermined value BV11 (= EV16 (ISO100)), it can be identified as a scene including the sun. Set 4 in the Y register, transfer the aperture value AV ₀ stored in the Z ₁₄ register to the contents of Z ₀₆ , and output the metering output of the register Z ₀₄ .
By adding to PV ₄ , Z ₁₄ ← [BV ₄ ] = [AV ₀ ] + [PV ₄ ] (41) is obtained. After that, Z _1Y ← [BV _Y ] = [AV ₀ ] + [PV _Y ] (Y = 0, 1, ..., 3) until the Y register is decremented by 1 and becomes negative (4
By repeating 2), the five brightness values BV _{4 to} BV ₀ are stored in the registers Z _{14 to} Z ₁₀ .

FIG. 16 is a flow chart of the cut processing subroutine shown in FIGS. 13 and 14. First, in step a, a data memory [C] = used for the later-described calculation
M [7,4], [L] = M [7,5], and [CL] =
Clear M [7,6]. At step b, the Y register is set to 4.

At step c, a comparison corresponding to BV _Y > $ 33 (Y = 0,1,2, ..., 4) (43) (where $ 33 corresponds to BV11) is performed. If Eq. (43) holds, proceed to step d. If not, jump to step h.

At step d, if [C] ≧ 2 (44) holds, go to step g, otherwise go to step g.
Go to step e. Since [C] = 0 at the beginning,
Go to step e.

In step e, BV _Y = 0 (Y = 0, 1, ..., 4) (45).

Next, at step f, the number of cuts [C] (that is, the number of photometric areas which are not adopted in the photometric calculation among the photometric areas Z _{0 to} Z ₄ ) is incremented by one. In the previous state, if the number of cuts is 0, it is 1, and if it is 1, it is 2.

At step g, BV _Y = $ 33 (46).

Since the scene in which the equation (43) is satisfied includes the sun, in step e, the photometric area including the sun is cut so that it is not calculated in order to ignore it. However, if the number of cuts [C] increases, it cannot be ignored. Therefore, in step g, the photometric output is also included in the calculation, so that a limit is given by the formula (46).

On the contrary, when the brightness is low, the photometric output is compared with the photometric lower limit PVth of $ 00 in step h.

PV _Y = $ 00 (47) If this equation (47) is satisfied, the process proceeds to step i, otherwise jumps to step n.

At step i, the number of cuts [L] due to the lower limit of photometry
For [L] = 2 (48), determine whether If yes, go to step l, otherwise go to step j. The beginning is 0
Since it has been set to step j, proceed to step j.

In step j, the photometric area is cut in the same manner as when the equation (43) holds. At the next step k, the number of cuts [L] is incremented by one.

On the other hand, in step 1, [BV _Y ] = [PVth] (= 0) + [AV ₀ ] (49).

After that, 1 is set in the memory [CL] indicating that the processing of the equation (49) has been performed, and the number of cuts [L] due to the lower limit of photometry is increased by 1. Next, when [L] = 3, this process is not performed.

The region below the photometry lower limit PVth is ignored in step j, but cannot be ignored if there is a certain number or more. Therefore, in step k, the region below the photometry lower limit PVth is regarded as the same value PVth and processed.

Finally, in step n, the Y register is decremented by 1 and repeated until the same register becomes negative, whereby the cut processing of BV ₄ to BV ₀ is performed.

The details of the subroutine for calculating the average luminance value in FIGS. 13 and 14 are omitted, but the following processing is performed. The number N of effective photometric areas is determined by [C], [L], and [CL] obtained by the cut processing subroutine of FIG. 16 N ← 5-C−L + CL 5 luminances Sum of values (as [SUM], M [4,7],
M [3,7], and divided by M using the [2,7]) the effective number N, is stored in register Z ₁₈ obtains an average luminance value BV _M.

When the multi-photometry calculation of FIG. 13 is performed with the above configuration, the following features occur. For example, if an F1.4 lens (AV ₀ = 1) is attached and the photometric output is $ 36, the BV ₀ will be $ 39. Then, BV ₀ is cut from the equation (43), but since $ 39 is stored in the BV ₀ (*), the equation (34) can be calculated. BVans (= BV _M)
= $ 2D, from equation (34), Δ ← $ F4 ← $ 2D ← $ 39. $ F4 is an amount equivalent to -4 [EV], and when exposure control is performed, it is 4 [E
V] Corrected exposure is performed on the over side.

When performing the multi-metering photometric calculation shown in FIG. 14, the result is as follows.

If the photometric output PV ₀ with the F1.4 lens attached is $ 3F, the processing of equations (36) and (37) is performed. Therefore, the correction amount is Δ = − (4 + AV ₀ ) = − 5 (50). Similarly, in the case of an F2.8 lens (AV ₀ = 3), the correction amount Δ is -7. By doing so, it works to control to the same brightness value when the upper limit of photometry is reached. When the photometric output exceeds the upper limit value, a constant correction amount Δ (-5
Or because it is controlled by -7), it is always corrected to the over side as compared with the case where it is controlled only by the photometric output of the central part (Δ = 0), so the effect of multi-photometry is maintained. Can be done. On the other hand, in the case of FIG. 13, when the photometric output PV _{0 at} the center is $ 3F, the F1.4 lens ([A
BV ₀ (*) with V ₀ ] = $ 03) is $ 42.
Yotsute correction amount delta = BV _M - Because $ 42 to become BV _M is not greater than Yotsute $ 33 Katsuhito processing (43) below, the correction amount delta is $ 33- $ 42 = $ F1 (= - The correction amount is -5 [EV] or more. -5 [EV]
But (50), but it corresponds to the correction amount of formula can be a Yotsute 5 [EV] or more correction amount BV _M. Since an unstable factor such as the upper limit of photometry increases, it becomes possible to perform stable control when the correction amount is constant as in the embodiment of FIG.

As shown in FIG. 14, when the photometric output at the central portion is below the photometric lower limit, the correction amount is set to 0, but the idea is the same. The photometric output is wider than the peripheral photometric output by using two photometric elements. The photometric output of the central part is below the photometric lower limit, so the control is performed only by the photometric output of the central part. are doing.

(Effect of the invention) As described above, in the present invention, when the photometric output before the release is started is at the photometric limit, the photometric output is corrected so that the exposure amount exceeds the fixed amount, so that shutter control is possible. In general, for a high-brightness subject, it is possible to obtain an optimal photograph by setting the exposure amount to a slight degree, so that proper photography can be performed.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) are explanatory views of an example of division of a photometric area by multi-photometry, FIG. 2 is a sectional view of a photometric optical system, and FIG. 3 is an SPD realizing the division of FIG. 1 (b). Pattern diagram, No. 4
FIG. 5 is a block diagram of an embodiment of the present invention, FIG. 5 is an internal configuration diagram of the MCU 122 used in FIG. 4, FIG. 6 is a flow chart of the MCU 122, FIG. 7 is a flow chart of an interrupt processing routine of the MCU 122, FIG. 8 is a flow chart of the information input subroutine of FIG. 6, FIG. 9 is a flow chart of the multi-photometric calculation subroutine of FIG. 6, and FIG. 10 is a flow chart of the S mode calculation subroutine of FIG. FIG. 11 is a flow chart of a subroutine of the A mode operation of FIG.
6 is a flow chart of the subroutine of the display calculation of FIG. 6, FIG. 13 is a flow chart of the subroutine of the multi-photometry calculation of FIG. 6, and FIG. 14 is a subroutine of the multi-photometry calculation of the embodiment of the present invention of FIG. 15 is a flowchart of the BV conversion subroutine shown in FIGS. 13 and 14, and FIG. 16 is a flowchart of the cut processing subroutine shown in FIGS. 13 and 14. (Description of symbols of main parts) 10 ... Photodiode (SPD), 100-104 ... Photometric circuit, 105-109 ... Setting means, 120 ... Analog switch circuit, 121 ... A / D converter, 122 ...... Micro computer unit (MCU), 123,124 …… D / A converter, 155
...... Aperture control means, 165 ...... Memory capacitor, 180 ......
Shutter Magnet

Claims (1)

[Claims] 1. An automatic exposure control apparatus of a camera aperture metering system for controlling a shutter speed by a photometering output after rephotometry by a photometering device after the aperture stop of a photographing lens is started after a release and is controlled to a predetermined aperture value. Determining means for determining whether or not the photometric output before the release is started is a photometric limit, and the photometric so that the exposure amount exceeds a certain amount when the photometric output is determined to be equal to or more than the photometric limit value by the determining means. An automatic exposure control apparatus of a narrowed-down photometry system, comprising: a correction means for correcting an output, wherein a shutter speed is controlled by the corrected photometric output after the light is narrowed down to a predetermined aperture value.